1. Field of the Invention
The present invention relates to a mounting structure of a chip component, and more particularly relates to a mounting structure of a chip component to be installed in an electronic module having a mold structure. The present invention also relates to an electronic module using the mounting structure of a chip component.
2. Description of Related Art
In recent years, with increase in demand and multifunction for a mobile device such as a smartphone and a tablet computer, it has been required to downsize a component to be installed and to shorten the component in height. For this reason, there is an increasing demand for an electronic module product having intensive functions. A chip component to be installed in the electronic module needs to be mounted with a narrow pitch with a high density to meet the demand of downsizing the electronic module (see Japanese Patent Application Laid-open No. 2010-21192), and is required to exhibit high reliability when employing a mold structure or a shield structure.
A method of forming a solder fillet on a side surface of the chip component is generally known as a method of mounting a chip component. However, in the case of the mold structure and a combination of the mold structure and the shield structure, a method of forming a solder fillet on an inner side (an electrode) of the chip component with a partially formed solder resist below the chip component has been introduced in order to secure the reliability (See Japanese Patent No. 4341321).
However, in Japanese Patent No. 4341321, due to a small clearance between the top of the partially formed resist below the chip component and a body of the chip component, it is difficult to remove residual flux and to fill molding material, which may cause solder flash or peeling particularly in a reflow test after a water absorption process.
In most cases, only a land pattern for installing a component is formed on a surface layer of a ceramic-based substrate represented by an LTCC (Low Temperature Co-fired Ceramics), and no solder resist is formed on the surface layer. On the other hand, except for some substrates, a wiring pattern and an inter-land connection pattern as well as the land pattern for installing a component are formed on a surface of a resin-based substrate represented by a PCB (Printed Circuit Board). This is because a process of manufacturing the PCB employs a build-up process. From the aspect of cost, the number of processes, and thickness, these patterns are covered by the solder resist in most cases. However, in a structure of molding chip components mounted with a high density, particularly between the components, a portion covered by the solder resist is likely to cause a problem of peeling and cracking.